TI Definitions
Absolute Zero: At absolute zero, a hypothetical temperature, all molecular movement stops. All actual temperatures are above absolute zero. Absolute zero would occur at -273.16 degrees Celsius, -459.69 degrees Fahrenheit, or 0 Kelvin.
Absorption: The process by which a material takes in thermal energy from an outside source
Active Emitter: Emits heat at a low to medium rate on its own, like people and pets.
Anomaly: Any irregularity, such as a thermal anomaly on an otherwise isothermal surface. Any indication that deviates from expectations.
Apparent Temperature: The target surface temperature indicated by an infrared point sensor, line scanner, or imager before temperature corrections are made.
Awareness-Level Thermal Imager: A thermal imager that does not meet the NFPA recommendations of screen size, FOV, resolution, and refresh rate. Used in monitoring conditions and egress.
Blackbody: A theoretical object that radiates the maximum amount of energy at a given temperature and absorbs the entire energy incident upon it.
Bolometer, Infrared [Micro-Bolometer] - A type of thermal detector commonly used in uncooled radiometers.
Decision-Making Thermal Imager: A high-performance thermal imager capable of providing detailed, reliable, and rapid thermal data for critical fireground decisions, such as search and rescue or fire attack, rather than just basic situational awareness. A thermal imager that meets or exceeds all NFPA recommendations for screen size, FOV, resolution, and refresh rate is a decision-making thermal imager.
Direct Emitter: Emits heat at a high rate on its own, like fire or the sun.
Direct Temperature Measurement: (AKA Spot Temperature or Numeric Temperature Indicator) is a feature that displays the approximate temperature of a specific, targeted surface within the thermal image
Distance to Spot Ratio: A measurement of the area from a specific distance. A 10:1 ratio indicates that the surface temperature measurement taken at 10 feet covers an area of 1 square foot.
Display: The visual output screen that presents infrared radiation data as a grayscale or colorized image
Emissivity: The efficiency of a material's surface in emitting infrared radiation, rated on a scale from 0.0 to 1.0
Emitter: Any substance that gives off (emits) heat
Field of View: The total angular extent of the scene captured or visualized by the thermal imager at any given moment. It is a measure of the camera's viewing angle, usually expressed in degrees (e.g., horizontal and vertical angular degrees).
Focal Plane Array [FPA]: Measures electromagnetic energy received by the detector elements, converting incoming radiation (often infrared or thermal) into electrical signals to create images.
Gain: The automatic adjustment of a thermal imager’s sensitivity based on the thermal energy (heat) present in the scene.
Heat Color Reference Bar: A mandatory, standardized visual indicator on thermal imagers that translates scene temperatures into a consistent color palette.
Hertz (Hz): A unit for measuring frequency. One Hertz equals one cycle per second. The higher the Hz, the better the refresh rate.
High Emissivity: The ability of a surface to efficiently emit thermal infrared radiation, with a value closer to 1.0 on a scale of 0 to 1. A high-emissivity material has greater absorption and lower reflection, and a rougher surface than a low-emissivity material.
High Gain: The operational setting of a thermal imager designed to maximize
sensitivity in lower-temperature situations, typically identifying smaller temperature differences. It prioritizes fine details over heat detection. The thermal imager starts up in high gain.
Infrared [IR]: The infrared spectrum is loosely defined as that portion of the electromagnetic continuum extending from the red
visible (0.75 mm to about 1,000 mm). Because of instrument design considerations and the infrared transmission characteristics
of the atmosphere, however, most infrared measurements are made between 0.75 and 20 mm.
Investigative Mode: A mode in your thermal imager that the palette colorizes lower heat to make it easier to locate flow paths and lower-heat objects. This is not an NFPA requirement, but it is invaluable in many situations
Latent Thermal Prints: Residual thermal signature left behind on a surface that has recently been in contact with a heat source (such as a human body)
Low Emissivity: A material’s property of emitting less radiant infrared energy compared to a material with high emissivity. Low emissivity indicates a surface that reflects more infrared radiation, thereby reducing heat transfer. A low-emissivity material has greater reflectance and lower absorptance. It has a smooth, shiny surface.
Low Gain: The least thermally sensitive operational mode of a thermal imager, designed to increase the camera's temperature range. It is designed to detect higher temperatures without saturating the sensor. It prioritizes heat detection over fine details.
Microbolometer: A specific type of uncooled infrared detector used as the "engine" or sensor in thermal imagers to translate thermal radiation into electrical signals for image processing
Micron [Micrometer] [m or, mm ]: One millionth of a meter; a unit used to express wavelength in the infrared.
Minimal Focal Distance: The closest distance the lens can be to an object while still producing a sharp, in-focus thermal image
Mixed Gain: High and low gain are displayed on the same display. It works by changing the gain pixel by pixel, currently only on Seek TI.
Modes: Different mode selections on your camera may include different palettes, features, and temperature readings. Some examples include TI Basic, search-and-rescue mode, inverse mode, cold-spot mode, multicolor palette mode, super red-hot mode, and survey mode.
Noise Equivalent Temperature [Difference], NET[D]: The temperature difference that is just equal to the rms noise signal; a measure of thermal resolution (thermal sensitivity), but not taking into account target size, characteristics of the display, and the
subjective interpretation of the operator.
NUC (Non-Uniformity Correction): This process corrects minor detector drift caused by changes in the scene and environment. It is normal to hear a click, and the image may freeze momentarily. Also called shuttering, this is when the frame freezes and resets.
Numeric Temperature Indicator: AKA Spot Temperature or Digital Temperature Measurement, is a feature that displays the numeric approximate temperature of a specific, targeted surface within the thermal image
Palette: A color mapping mode that translates infrared radiation (heat) detected by a sensor into a visible image. These palettes assign specific colors or grayscale tones to different temperature values, allowing users to identify heat distribution, anomalies, and contrast between objects and their background.
Pixel: Represents the individual detector elements on the sensor array that measure infrared energy, forming a grid. Ex 320x240 Each pixel detects heat from a specific part of a scene, creating a corresponding color map of temperatures.
Passive Emitter: An emitter that cannot generate heat on its own but can absorb and re-emit heat. Examples include a chair or a couch.
Qualitative Thermal Imaging: Focuses on identifying thermal patterns, gradients, and relative temperature differences rather than on exact temperature measurements
.
Quantitative Thermal Imaging: Focuses on obtaining exact temperature measurements of an object or area. Think of quantity as a number.
Radiation: Heat transfer through electromagnetic waves, without objects or gases carrying it along
Reflectivity: The amount of infrared radiation reflected by a surface, which is not related to the surface material itself.
Refraction: The redirection of thermal radiation as it passes between materials of different densities, caused by a change in its speed as it passes from one medium to another (e.g., air to lens).
Spot Temperature: AKA Numeric Temperature Measurement or Digital Temperature Measurement indicator is a feature that displays the approximate temperature of a specific, targeted surface within the thermal image
Thermal Contrast: The difference in infrared radiation (heat) between a target object and its surrounding background. The greater the object’s temperature difference compared to the background, the greater the thermal contrast.
Thermal Inversion: Occurs when a scene’s ambient temperature exceeds the temperature of the firefighter or victim, causing cooler subjects to appear dark grey or black instead of the expected white hot
TI Basic: The mandatory, default color palette and operational mode designed for rapid interpretation of the thermal environment
TI Basic +: An operational mode for thermal imagers that allows for advanced features, enhancements, and innovations beyond the mandatory, simplified TI Basic mode. This mode requires advanced training per NFPA.
Transmissivity: The ability of a material to allow radiation to pass from one side to the other without being absorbed or reflected.